The invention concerns a system for storing and providing lancets for collecting body fluids, in particular for blood collection, and it concerns a corresponding working process for the system for the purpose of collecting body fluids and in particular for blood collection.
The examination of samples of body fluids and in particular blood samples in clinical diagnostics enables an early and reliable detection of pathological states and a specific and well-founded monitoring of body states. Medical blood diagnostics always requires the collection of a blood sample from an individual to be examined. Whereas several milliliters of blood are collected from a person to be examined by venipuncture for analysis in hospitals and by physicians in private practice in order to carry out many laboratory tests, nowadays only a few microliters of blood and sometimes even less is often sufficient for individual analyses which are specific for one parameter. Such small amounts of blood do not require venipuncture. On the contrary it is sufficient to obtain blood by pushing a sterile, sharp lancet through the skin e.g. into the finger pad or earlobe of the person to be examined in order to collect a few microliters of blood or even amounts of blood in the nanoliter range for the analysis. This method is particularly suitable when it is possible to carry out the analysis of the blood sample immediately after the blood collection.
Lancets and corresponding devices (so-called blood collection instruments, blood lancet devices or lancing devices) which enable a substantially pain-free and reproducible blood collection are available especially in the so-called home-monitoring field i.e. where medical laymen themselves carry out simple analyses of the blood especially for the regular blood collection by diabetics which has to be carried out several times daily to monitor the blood glucose concentration. Examples of lancets and lancing devices are the commercially available devices (lancing devices) and lancets Glucolet(copyright) from the Bayer AG Company and Softclix(copyright) from Roche Diagnostics GmbH. Such lancets and devices (lancing devices) are for example the subject matter of EP-A 0 565 970.
In the systems that are available at present the lancets for use in lancing devices are usually provided in a loose form. For each lancing process the user manually removes a lancet from a pack, for example a cardboard box or a tube containing a plurality of lancets (usually in a disordered arrangement and loosely packed). Subsequently the lancing device is prepared for receiving the lancet by for example unscrewing or pulling off a protecting cap to expose the lancet holder of the lancing device. The lancet removed from the pack is manually inserted into the lancet holder of the lancing device and fixed there. Then the protective cover has to be manually removed from the lancet. Subsequently the lancing device is sealed again with its protecting cap. The cap ensures that the lancet is no longer accessible from outside. It usually has an opening through which the lancet tip can pass during the actual lancing process. Finally the lancing device is tensioned and is available for the lancing process to collect blood.
The many manual operating steps in conventional lancet systems (lancet and lancing device) are felt to be disadvantageous by the user and are particularly problematic when perception is limited in a hypoglycaemic state. Moreover the user is not prevented from using a once inserted lancet several times for lancing and collecting blood. Multiple use of a lancet must be prevented for hygienic reasons especially when the lancet is used by more than one person which for example may be the case in doctors practices or hospitals or if misuse for example by children cannot be excluded. On the other hand the repeated use of lancets also leads to increasing pain for the user since the lancets are designed for single use and rapidly become blunt when used several times. Furthermore with the lancing devices and lancets of the prior art there is a risk that lancets will be inserted improperly into the lancing devices. Furthermore a user can be accidentally injured when the lancets and lancing devices are used improperly.
There have therefore been no lack of attempts to eliminate the said disadvantages. Lancing devices are known from U.S. Pat. No. 5,514,152, U.S. Pat. No. 5,152,775, U.S. Pat. No. 4,794,926 and U.S. Pat. No. 5,035,704 which store several lancets and can use these individually and in succession for lancing processes. After the lancing process the lancets can be removed individually from the device. Storage in a magazine and the ability to automatically dispense lancets helps to avoid mistakes when placing a lancet in a lancing device. In order to carry out the lancing movement, the lancet in the blood collection device (lancing device) must firstly be moved or deflected in a lancing direction (i.e. it""s tip moves towards the body region to be pierced) and subsequently retracted as rapidly as possible into its initial position. In conventional lancet systems such as those described in EP-A 0 565 970 the part of the lancet that faces away from the tip is enclosed as tightly as possible by a lancet holder which is part of the lancing device and is moved in the lancing direction (forwards) as well as back to the starting position (backwards). The forwards and backwards movement is accomplished by a single drive mechanism which is often driven by a spring.
An automatic change of lancets by for example using a lancet magazine is difficult to realise with such a system in which it is necessary to enclose the lancet in a lancet holder. Moreover the lancet must have a lancet body which is adapted to the lancet holder and makes a firm connection between the lancet and holder especially to ensure the backwards movement. Consequently the lancets are often voluminous and their storage in a magazine would lead to large dimensions of the lancet system.
The lancet system described in U.S. Pat. No. 4,794,926 utilizes the elastic force of a leaf spring which is part of the lancet to move the lancet forwards and backwards. However, this propulsion method is unsuitable for essentially needle-like lancets.
A lancet system is known from U.S. Pat. No. 5,578,014 in which the drive of the lancet for the forwards movement operates independently of the drive for the return movement. The return movement is effected by a spring driven plunger which is part of the lancing device and acts on the lancet from behind i.e. on the end facing away from the tip. The return movement is driven by a spring which is incorporated in the lancet. Similar systems are described in U.S. Pat. No. 5,029,583 and DE-A 198 55 465. A disadvantage of this variant is that each lancet has to be equipped with its own spring which makes the manufacturing process complicated and expensive. Moreover it is very difficult to miniaturize the system.
Attempts to reduce the manufacturing costs for such lancets which are mass-produced articles (so-called disposables) often results in the obligatory use of cheap return springs. In this case the material properties are often subject to large variations which also means that there are also considerable variations in the return speeds. This can have a negative impact on the pain sensation during the lancing process.
The object of the invention is therefore to eliminate the disadvantages of the prior art. In particular it is an object of the present invention to provide a system for collecting blood or other body fluids which provides a plurality of lancets in the smallest possible space. This object is achieved by the subject matter of the invention.
The invention concerns a system for storing and providing lancets to collect a body fluid and in particular for blood collection. The invention also concerns a process for temporarily extending the tip of an essentially needle-shaped lancet from a system for storing and providing lancets to collect body fluids and in particular for blood collection. The invention also concerns a lancet magazine, a lancing device, and a lancet.
The system according to the invention comprises: i) a plurality of essentially needle-shaped lancets; ii) a drive unit which has a drive element such as a plunger which, in order to carry out a lancing process, is moved from a resting position into a lancing position; iii) a storage area to store the lancets; iv) a withdrawal area to guide at least the tip of the lancet out of the system during the lancing process and v) a transport unit which can transport lancets from the storage area into the withdrawal area. The drive element is arranged in the system according to the invention in such a manner that in the withdrawal area it can act on the lancet located there to carry out a lancing process for example by striking one end of the lancet like a hammer or a firing pin and thus moving the lancet from its resting position into a lancing position. In addition the system has a return device in the withdrawal area which can interact with the lancet located in the withdrawal area in order to move the lancet after completion of the lancing process from its lancing position into its resting position. In this process the drive unit and the return device act independently of one another on the lancet.
The system according to the invention comprises a plurality i.e. at least two essentially needle-shaped lancets. xe2x80x9cEssentially needle-shapedxe2x80x9d means that the lancets have a metal lancet needle with a tip which can be optionally ground. In this connection it is important that the lancet itself has no spring or such like which returns it to its initial position after the lancing movement. A central retraction device in the system returns the lancet.
A plastic lancet body made of an injection mouldable material can be injected onto the lancet needle in order to facilitate handling of the lancet in the system such as to transport the lancet from its storage position into the withdrawal position or to grip the lancet by the retraction device. The blunt end of the lancet needle i.e. the end facing away from the tip can also be compressed, flanged, bent or serrated to facilitate gripping of the lancet by the retraction device.
The lancet body is usually a plastic component which is mounted around the lancet needle and encloses it. The lancet body facilitates gripping of the lancet needle and can simply have a special shape adapted to the geometry of the lancing device. Hence the external shape of the lancet is essentially determined by the lancet body.
The tip of the lancet needle is preferably surrounded by a protective sheath in the unused state to ensure its sterility. This can be composed of the same material as the lancet body and then usually forms a single unit with this. The protective sheath can be separated from the lancet body and removed from the tip of the lancet needle before using the lancet. A predetermined breaking point is preferably located between the lancet body and protective sheath for this purpose.
The lancet of the invention comprises a needle (lancet needle) with a tip. The needle is usually several millimeters (mm) to a few centimeters (cm) in length and has an elongate shape. Needles typically have a cylindrical shape since this needle shape is particularly easy to manufacture; however, other needle shapes having different designs are also possible. The tip region of the needle comprises the needle tip which is inserted into the tissue when the lancet is used as directed. Hence the tip of the lancet needle is the part of the lancet which comes into contact with and may injure the skin of the individual to be pierced and thus causes a body fluid and in particular blood or interstitial liquid to flow out.
The tip of the lancet needle can for example be rotationally symmetrical as is generally the case for sewing needles. However, it has proven to be advantageous to provide the needle tip with one or several bevels. The edges formed in this manner which are slanted relative to the longitudinal axis of the needle and converge to form a tip act as a sharp cutting edge in the piercing process and make the piercing process less painful than is the case with rotationally symmetrical needles. The lancet needle of the lancet according to the invention is manufactured from a material which is hard enough to withstand mechanical stress without deformation during the piercing process, during the processing steps for its manufacture or other stresses which may occur. In addition the material must be such that no particles break off or become detached during the piercing process. Finally it must be possible to machine the needle in such a manner that the needle tip is sufficiently pointed and the edges of the needle tip can optionally be ground to a sufficient sharpness. Materials that are very suitable for the lancet needle are above all metals and of these especially high-grade steels. However, needles made of ceramics, silicon or plastics are also conceivable. High-grade steel needles are particularly preferred.
In a preferred embodiment at least the tip of the lancet needle of the lancet according to the invention is surrounded by a plastic body which is referred to in the following as the lancet body. In this connection it is preferable that the lancet body is made of an elastic material in the area of the tip of the lancet needle. At least the tip of the lancet needle is completely surrounded on all sides by this elastic material i.e. it is embedded in it and thus sealed from the surroundings. The elastic material of the lancet body which in various embodiments can completely or only partially form the lancet body is characterized in that it is soft, deformable and can be pierced by the tip of the lancet needle without damaging the tip. In the lancing process the lancet needle is moved along its longitudinal axis relative to the lancet body and its tip emerges from the lancet body in order to thus be able to pierce the skin of the individual to be examined in order to collect blood. Another important property is that the elastic material again closes around the tip of the lancet needle when the lancet needle is retracted into the lancet body. After the lancing process the lancet needle can be returned to its initial position relative to the lancet body by reversing the piercing movement in a preferred embodiment and in this position the tip is again completely enclosed on all sides by the elastic material of the lancet body.
The elastic material of the lancet body which completely encloses the tip of the lancet needle ensures the sterility of the lancet needle tip before use and preferably until immediately before use and optionally encloses the lancet needle tip after use. Consequently the elastic material is impenetrable to germs. In addition the elastic material represents a mechanical protection for the lancet needle tip and thus also prevents unintentional injury on the lancet needle tip.
Suitable elastic materials for the lancet body of the present embodiment have proven to be rubber, caoutchouc, silicons, elastomers and in particular thermoplastic elastomers. These have important properties for the present invention: they are soft, deformable, can be pierced by the lancet needle without damaging the tip and they form a tight seal around the used lancet needle tip. Furthermore they can be used for injection moulding processes which enables the lancets to be mass-produced in large numbers.
During the piercing process the lancet needle is moved relative to the lancet body. In this process the latter is preferably fixed in its position by the lancing device or the lancing instrument. The lancet needle can contain suitable elements for the purpose of driving it in a forward and/or backward direction. In particular it can have a special shape such as a needle head, a flange, a bend or a recess at the end opposite to the tip, or it can have an additional lancet body which is engaged by the drive element of the lancet system in addition to the lancet body which encloses the tip.
The form of the needle or of the additional lancet body can interact in a suitable manner with a corresponding drive device and/or retraction device in the lancing apparatus (lancing device).
In order to increase the stability of the elastic material it is possible to combine it with a stiff material such as a stiff plastic material. In this case the outside of the elastic material which does not come into contact with the lancet needle can for example be stabilized with a layer of a stiff material such as a stiff plastic. It is also possible to manufacture only the lancet needle tip region of the lancet body from an elastic material and to use a conventional stiff plastic in the other regions of the lancet body. In this connection the elastic material and the stiff material can be glued together or joined together in an injection moulding process for example in a two-component injection moulding process. The stiff material of the lancet body mechanically stabilizes the elastic material during the lancing process and simplifies the fixing of the elastic part of the lancet body in the lancet system during the lancing process.
In a further preferred embodiment the lancet contains a lancet needle comprising a tip and a hollow body which surrounds at least the tip of the lancet needle, the tip region of the lancet needle being movable in the hollow body and the hollow body being sealed by a foil that can be pierced by the tip of the lancet needle during the lancing process and can optionally reseal after the tip of the lancet needle has been retracted into the hollow body.
The regions of this hollow body which do not come into contact with the lancet material are preferably manufactured from a stiff, preferably injection mouldable material.
During the lancing process the lancet needle is moved relative to the hollow body which represents the lancet body. The holder and drive for the lancet needle and the attachment of the lancet body can be realised as described above by suitable constructional measures.
The elastic material which comprises a part of the hollow lancet body is pierced by the lancet needle tip during the lancing process and optionally reseals after the lancet needle tip has been retracted again into the hollow body and thus seals the hollow body. Hence the lancet needle tip is sealed in a sterile manner in the hollow body until immediately before use and is hygienically enclosed in it after use.
The lancet of this embodiment can in addition to the lancet body which encloses the tip of the lancet needle have a further lancet body which interacts with suitable elements of a lancing device during the lancing process. In addition the lancet needle can have a special shape; for example it can have a head at the end opposite to the tip to facilitate the propulsion of the lancet.
In a preferred embodiment the essentially needle-shaped lancet has a pinhead at the end opposite to the tip. In the system according to the invention this can interact with the retraction device such that the retraction device can move the lancet back into the starting position (resting position) after the lancing process. The pinhead can, as is for example the case with pins, be an integral part of the lancet needle. The lancet needle is then preferably manufactured from one piece in particular from one metal. However, it is also possible that the pinhead is a separate part connected to the needle such as a plastic part injected onto the needle. The pinhead can be a flattened end of the lancet needle provided with a bead, such as the head of a pin or the striking surface of a nail. Alternatively the pinhead can be a terminal thickening of the lancet needle or a ring surrounding the lancet needle and sealing tightly against it or a disk placed on the blunt end of the needle.
The system according to the invention also contains a drive unit for the lancet. The drive unit contains a drive element such as a plunger or a hammer which is moved from a resting position into a lancing position in order to carry out a lancing process. The drive element is arranged in the system according to the invention in such a manner that in the withdrawal area it can act on the lancet located there to carry out a lancing process for example by striking one end of the lancet like a hammer or a firing pin and thus moving the lancet from its resting position into a lancing position. In connection with the present invention it is important that although the drive unit causes the forward movement of the lancet i.e. the movement which brings the lancet from its resting position into the lancing position, it does not cause the reverse movement of the lancet. The drive unit can be designed in a known manner and for example be equipped with a spring drive and optionally gear elements. Such drive elements are in principle known to a person skilled in the art and can be easily realised.
Many embodiments of suitable drives are known from the prior art. The drive plunger executes a push movement and subsequently a retraction movement. During the push movement the lancet is also moved forwards i.e. in its lancing direction. During the retraction movement of the drive element it no longer acts on the lancet. This allows the lancet to also move backwards. Since the lancet is coupled to a retraction device according to the invention this can also take over the return movement of the drive plunger. This is for example appropriate when the drive is a simple cam like those known from the valve drives of engines. This is also the case for simple spring-loaded plungers which are propelled forwards from the tensioned position and strike the lancet and hence move it forwards. In contrast in the case of a constrained control of the movement of the drive element i.e. when the forward as well as the return movement of the drive element is achieved by a suitable drive, the return unit only moves the lancet.
The system according to the invention is used especially to store and to automatically provide lancets for lancing processes and to carry out lancing processes. It therefore also has a storage area to store the lancets. For example the system can have a space for holding a lancet magazine. At least the unused lancets can be accommodated in the storage area. However, it is preferably also possible to store the used lancets until their disposal. The system can also have separate storage areas for unused and used lancets.
In addition the system of the present invention has a withdrawal area for guiding at least the tip of a lancet out of the system during the lancing process. In order to carry out a lancing movement a lancet located in the system is firstly transported from the storage area into the withdrawal area. Here the lancet is then in a position which can, on the one hand, be driven by the drive element of the drive unit in a forward direction i.e. in the direction of the lancing movement and in which it can, on the other hand, interact with the retraction device in a suitable manner in order that it can be brought back into its starting position after the lancing process. Suitable constructional measures should ensure that the lancet in the withdrawal area can interact in particular with the drive element as well as with the retraction device. Furthermore the system according to the invention has an opening in the withdrawal area which enables the lancet tip to protrude from the system during the lancing process.
A further component of the system according to the invention is a transport unit which can transport lancets from the storage area into the withdrawal area. The transport unit can be driven and/or controlled manually or automatically. The exact type of transport unit is not important for the present invention and can vary depending on the exact manner of storage of the lancets in the system. The transport unit can be driven manually or with the aid of a spring or motor.
In addition the system has a central retraction device in the withdrawal area which can interact with the lancet located in the withdrawal area in order to move the lancet from the lancing position into its resting position after the lancing process has been carried out. The drive unit and the retraction device act independently on the lancet. The retraction device has a spring mechanism in a preferred embodiment which particularly preferably comprises a leaf or spiral spring. Alternatively the retraction device can contain a deformable elastomer for example a compressible rubber block which relaxes when it is unloaded and thus causes the return movement. Particularly preferred embodiments of the retraction device as well as their special interaction with the lancets are described in conjunction with the figures (see below). In contrast to the state of the art the system according to the invention only has a central retraction device which means that individual lancets do not have a return spring or such like to move them back into the starting position after the lancing movement has been carried out.
It will be apparent that the lancets, drive unit and return device of the system according to the invention have to be mutually compatible. For example the form of the lancet can fit that of the retraction device at least in the return direction. This can be achieved by shaping the lancet like a sliding block in a machine tool which engages in a corresponding T slot or a simple slot in sheet metal (cf. for example FIGS. 1A and 1B, further below). In order to transport the lancet further the drive mechanism can also be disengaged which enables the return mechanism to be designed as a spring-loaded fork that simply engages behind the thickened end of the lancet (see FIG. 3, further below). The slot in the return spring designed as a leaf spring can also be conically narrowed in the inlet of the lancet and become wider again in the outlet so that the lancet is only a smooth needle the middle of which, i.e. the constriction, is pinched on one side and is thus docked on to the return spring. The blunt plunger of the drive then moves the needle forwards, the spring returns it again when the plunger has retracted.
The lancets of the system according to the invention are preferably accommodated in a lancet magazine. This can be removed from the system after the lancets have been consumed and replaced by a new magazine. In this manner the user of the system can replace the used lancets by new ones in a simple manner.
The lancet magazine preferably also contains the retraction device for the lancets. This is especially advantageous when the retraction device has a spring mechanism: With each change of magazine the system is provided with a new unused drive spring for the return mechanism. Hence it is possible to largely avoid fatigue phenomena of the spring material. This enables the movement to be kept constant which in turn reduces pain during lancing. In addition in such an embodiment no interface is necessary between the retraction device and the instrument which holds the lancet magazine. The magazine and thus also the entire system containing the magazine can thus be constructed in a very compact manner.
The magazine according to the invention for lancets contains in addition to a plurality of essentially needle-shaped lancets, among others a storage area to store the lancets and a withdrawal area to extend at least the tip of a lancet from the magazine during the lancing process. In the withdrawal area of the magazine there is either a retraction device that can interact with the lancet that is located in the withdrawal area in order to move the lancet from the lancing position into its resting position after carrying out the lancing process or it allows engagement of a retraction device, which is for example contained in the lancing device. Details of the individual components of the lancet magazine essentially correspond to the statements made above in connection with the system according to the invention.
A preferred embodiment of the lancet magazine additionally contains a transport unit which can transport the lancets from the storage area into the withdrawal area. The transport device can preferably interact with an appropriate drive unit in a blood collection instrument (also referred to in the short form as lancing device) when the magazine is present in such an instrument. In this case the magazine can contain part of the drive gear for the transport unit whereas a drive motor for the transport unit is for example located in the blood collection instrument. Moreover it is also possible that the transport unit and in particular its drive motor and its gears are located completely in the magazine and only its control and optionally energy supply are outside the magazine.
An additional subject matter of the invention is a lancing device which is suitable for use in a system for storing and providing lancets to collect body fluids and in particular for blood collection as described above. Like the system according to the invention the lancing device comprises a drive unit which has a drive element (for example a hammer or a plunger) which is moved from a resting position into a lancing position in order to carry out a lancing process. In addition the lancing device has a storage area to store lancets and a withdrawal area to extend at least the tip of the lancet from the system during the lancing process. In addition the lancing device contains a transport unit which can transport lancets from the storage area into a withdrawal area. The drive element is arranged such that it can act in the withdrawal area on the lancet located there in order to carry out the lancing process and thus move it from a resting position into a lancing position. In one embodiment the lancing device has a retraction device in the withdrawal area that can interact with the lancet located in the withdrawal area in order to move the lancet from the lancing position into its resting position after carrying out the lancing process. Alternatively the lancing device can hold a lancet magazine described above in more detail which in turn contains a retraction device. The individual elements of the lancing device essentially correspond to the elements described above of the system according to the invention.
The process according to the invention is used to temporarily move the tip of an essentially needle-shaped lancet out of a system for storing and providing lancets in order to collect body fluids and in particular for blood collection. It is especially suitable for the system according to the invention described above. In the process according to the invention a drive element such as a plunger is moved from its resting position towards its lancing position. It thereby propels a lancet from its resting position until it reaches its lancing position. After the lancet has reached its lancing position it is returned to its resting position with the aid of a retraction device. The forwards movement of the lancet i.e. the movement from the resting position into the lancing position is thus effected by the drive unit and in particular the drive element; the return movement is effected by a separate retraction device that is independent of the drive unit. In this connection the retraction device can in addition to the lancet also return the drive element to its resting position.